Long-term positive affect (the core component of happiness or well-being) is a central criterion of mental health and has been found to be associated with numerous tangible benefits, such as enhanced physical health, heightened vocational and social functioning, superior coping skills, and even longer life. Although enhancing people's levels of positive affect thus appears to be a worthy scientific goal, a surprisingly modest amount of scientific research has focused on how well-being can be increased, let alone sustained. Moreover, the broad conclusion of the existing work is that the pursuit of happiness may be futile. Two major findings support this pessimism - the idea of a genetically -determined set point for well-being, and the notion of a hedonic treadmill. Both of these ideas suggest that, even after intensely positive life events or circumstantial changes, people are fated to return to their previous "baseline" of well-being. Nevertheless, emerging research findings give reason for optimism regarding the possibility of sustainable well-being increases. How can this paradox be resolved? The research question motivating this application is "By what mechanisms can a level of well-being higher than a person's genetically-determined set point be achieved and sustained?" We believe that durable increases are indeed possible and focus our investigation on identifying the mechanisms of sustainable change in long-term positive affect. [unreadable] [unreadable] Accordingly, we present a new conceptual model of well-being, which proposes that an individual's chronic happiness level is governed by three classes of factors - (1) his or her genetically-determined set point (or set range) for happiness, which is relatively immune to influence, (2) happiness-relevant circumstantial factors (such as location, income, and marital status), which are difficult but not impossible to change, and (3) intentional cognitive, motivational, and behavioral activities that can influence well-being, and are feasible but effortful to deploy. Seven longitudinal studies (8 mos. to 2 [unreadable] yrs.) are proposed, which comparatively examine the immediate and longer-term effects of applying three promising happiness-boosting activities: 'counting one's blessings," "visualizing best possible selves,' and 'committing acts of kindness." The studies will include undergraduate samples, as well as community adult, and immigrant South Korean and Russian samples. In addition, we will test whether the model can be applied to clinically depressed individuals, as most depression interventions have focused on remedying distress, rather than increasing well-being directly. Several moderators (dedicated activity enactment, optimal timing and variety of activity enactment, personality-activity fit, interpersonal support, and basic circumstances) and one mediator (accumulated positive daily experiences) of activity-based happiness increases will be examined. [unreadable] [unreadable]